The present invention relates to a process for producing an electrical supply rail intended for ensuring the electrical supply of a locomotive by means of an electricity collector member carried by said locomotive and moving against said rail, and to an electrical supply rail which can be produced by this process.
Mention may be made, as non-limiting examples, of locomotives capable of being supplied with electricity in this way, of some railroad vehicles, some funiculars and some carousels.
Such an electrical supply rail can be produced in the form of a solid section of a single electrically conductive material, but increasingly frequently it comprises two longitudinal mutually fixed electrically conductive components having substantially constant respective cross-sections defined particularly by respective mutually complementary continuous longitudinal faces mutually juxtaposed transversely in a relationship of electrical conduction.
One of these components forms a body for mounting the supply rail on supports, such as insulators, and can itself serve for mounting protective caps on the supply rail; its cross-section is generally far larger than that of the other component and is determined, on the one hand, as a function of the desired rigidity to be imparted to the supply rail and, on the other hand, as a function of the current to be conveyed by this; to reduce its weight for a specific cross-section, this mounting body is usually produced from aluminum or an aluminum alloy.
The other component forms a wearing plate intended for interacting with the electricity collector member carried by the locomotive, and for this purpose it is produced, for example, from stainless steel which is more resistant to wear than aluminum and its alloys, but is denser, or from copper or brass; the cross-section of this second component is limited to the value necessary for ensuring a specific minimum operating time before complete wear, and its form can vary according to the particular design of the current collector member; this form can, for example, be flat between two mutually parallel plane longitudinal faces, one of which forms the abovementioned face of juxtaposition with the mounting body and the other of which is intended for interacting with the current collector member in this case consisting of a slipper; it can be V-shaped when the current collector member is a roller, these examples being in no way limiting.
A known process for producing such a two-component electrical supply rail involves producing these components separately and subsequently fixing them mutually by means of crimping; for this purpose, when it is desirable to have a flat wearing plate, the mounting body, for example produced from aluminum or an aluminum alloy, is capped by means of a longitudinal section produced, for example, from stainless steel and having a U-shaped cross-section defined by a longitudinal web forming the wearing plate and by two wings without the function of interacting with the electricity collector member and, in practice, intended to allow a mutual crimping of this U-shaped section and the mounting body; a contact grease interposed between the U-section and the mounting body makes an electrical connection distributed between them.
This known technique, when employed to produce electrical supply rails with a flat wearing plate, has a disadvantage in that, probably because of vibration phenomena and the difference between the respective coefficients of thermal expansion of the mounting body and of the section forming the wearing plate, these tend to detach from one another, with the result that, despite the presence of the contact grease, the electrical current follows elongate paths in a way detrimental to the stability of the wearing plate in time; moreover, the disadvantage of this technique is that it requires the use of a quantity of the component material of the wearing plate far larger than would be necessary for this wearing plate alone, thereby increasing both the weight per linear meter and the cost price of the supply rail.
To overcome these disadvantages, a technique which has been proposed involves longitudinally extruding the mounting body, for example made of aluminum or aluminum alloy, in contact with a flat longitudinal section, for example made of stainless steel, running longitudinally at a speed corresponding to the extrusion speed and intended for forming the wearing plate.
This technique makes it possible to obtain an effective mutual fixing, especially in terms of continuity of mutual electrical contact, between the mounting body and the wearing plate and to limit the use of the component material of the wearing plate to just the quantity necessary for ensuring that this plate has a long lifetime. However, this technique is particularly costly to put into practice, especially because of the complexity and cost of the installations which it requires.
The object of the present invention is to overcome these disadvantages by improving the abovementioned known process involving producing separately the two longitudinal components of the rail, namely the mounting body and the wearing plate, and subsequently mutually fixing them.